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<a name="Background-Execution"></a>
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<hr>
<a name="Background-Execution-1"></a>
<h4 class="subsection">5.5.3 Background Execution</h4>

<a name="index-foreground-execution"></a>
<a name="index-background-execution"></a>
<a name="index-asynchronous-execution"></a>
<a name="index-execution_002c-foreground_002c-background-and-asynchronous"></a>

<p><small>GDB</small>&rsquo;s execution commands have two variants:  the normal
foreground (synchronous) behavior, and a background
(asynchronous) behavior.  In foreground execution, <small>GDB</small> waits for
the program to report that some thread has stopped before prompting for
another command.  In background execution, <small>GDB</small> immediately gives
a command prompt so that you can issue other commands while your program runs.
</p>
<p>If the target doesn&rsquo;t support async mode, <small>GDB</small> issues an error
message if you attempt to use the background execution commands.
</p>
<p>To specify background execution, add a <code>&amp;</code> to the command.  For example,
the background form of the <code>continue</code> command is <code>continue&amp;</code>, or
just <code>c&amp;</code>.  The execution commands that accept background execution
are:
</p>
<dl compact="compact">
<dd><a name="index-run_0026"></a>
</dd>
<dt><code>run</code></dt>
<dd><p>See <a href="Starting.html#Starting">Starting your Program</a>.
</p>
</dd>
<dt><code>attach</code></dt>
<dd><a name="index-attach_0026"></a>
<p>See <a href="Attach.html#Attach">Debugging an Already-running Process</a>.
</p>
</dd>
<dt><code>step</code></dt>
<dd><a name="index-step_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">step</a>.
</p>
</dd>
<dt><code>stepi</code></dt>
<dd><a name="index-stepi_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">stepi</a>.
</p>
</dd>
<dt><code>next</code></dt>
<dd><a name="index-next_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">next</a>.
</p>
</dd>
<dt><code>nexti</code></dt>
<dd><a name="index-nexti_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">nexti</a>.
</p>
</dd>
<dt><code>continue</code></dt>
<dd><a name="index-continue_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">continue</a>.
</p>
</dd>
<dt><code>finish</code></dt>
<dd><a name="index-finish_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">finish</a>.
</p>
</dd>
<dt><code>until</code></dt>
<dd><a name="index-until_0026"></a>
<p>See <a href="Continuing-and-Stepping.html#Continuing-and-Stepping">until</a>.
</p>
</dd>
</dl>

<p>Background execution is especially useful in conjunction with non-stop
mode for debugging programs with multiple threads; see <a href="Non_002dStop-Mode.html#Non_002dStop-Mode">Non-Stop Mode</a>.
However, you can also use these commands in the normal all-stop mode with
the restriction that you cannot issue another execution command until the
previous one finishes.  Examples of commands that are valid in all-stop
mode while the program is running include <code>help</code> and <code>info break</code>.
</p>
<p>You can interrupt your program while it is running in the background by
using the <code>interrupt</code> command.
</p>
<dl compact="compact">
<dd><a name="index-interrupt-1"></a>
</dd>
<dt><code>interrupt</code></dt>
<dt><code>interrupt -a</code></dt>
<dd>
<p>Suspend execution of the running program.  In all-stop mode,
<code>interrupt</code> stops the whole process, but in non-stop mode, it stops
only the current thread.  To stop the whole program in non-stop mode,
use <code>interrupt -a</code>.
</p></dd>
</dl>

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